Pancreatic Gene Expression Research Articles

Alterations of Pancreatic Islet Structure, Metabolism and Gene Expression in Diet-Induced Obese C57BL/6J Mice

The reduction of functional β cell mass is a key feature of type 2 diabetes. Here, we studied metabolic functions and islet gene expression profiles of C57BL/6J mice with naturally occurring nicotinamide nucleotide transhydrogenase (NNT) deletion mutation, a widely used model of diet-induced obesity and diabetes. On high fat diet (HF), the mice developed obesity and hyperinsulinemia, while blood glucose levels were only mildly elevated indicating a substantial capacity to compensate for insulin resistance. The basal serum insulin levels were elevated in HF mice, but insulin secretion in response to glucose load was significantly blunted. Hyperinsulinemia in HF fed mice was associated with an increase in islet mass and size along with higher BrdU incorporation to β cells. The temporal profiles of glucose-stimulated insulin secretion (GSIS) of isolated islets were comparable in HF and normal chow fed mice. Islets isolated from HF fed mice had elevated basal oxygen consumption per islet but failed to increase oxygen consumption further in response to glucose or carbonyl cyanide-4-trifluoromethoxyphenylhydrazone (FCCP). To obtain an unbiased assessment of metabolic pathways in islets, we performed microarray analysis comparing gene expression in islets from HF to normal chow-fed mice. A few genes, for example, those genes involved in the protection against oxidative stress (hypoxia upregulated protein 1) and Pgc1α were up-regulated in HF islets. In contrast, several genes in extracellular matrix and other pathways were suppressed in HF islets. These results indicate that islets from C57BL/6J mice with NNT deletion mutation develop structural, metabolic and gene expression features consistent with compensation and decompensation in response to HF diet.

Integrating gene expression and epidemiological data for the discovery of genetic interactions associated with cancer risk

Dozens of common genetic variants associated with cancer risk have been identified through genome-wide association studies (GWASs). However, these variants only explain a modest fraction of the heritability of disease. The missing heritability has been attributed to several factors, among them the existence of genetic interactions (G × G). Systematic screens for G × G in model organisms have revealed their fundamental influence in complex phenotypes. In this scenario, G × G overlap significantly with other types of gene and/or protein relationships. Here, by integrating predicted G × G from GWAS data and complex- and context-defined gene coexpression profiles, we provide evidence for G × G associated with cancer risk. G × G predicted from a breast cancer GWAS dataset identified significant overlaps [relative enrichments (REs) of 8-36%, empirical P values < 0.05 to 10(-4)] with complex (non-linear) gene coexpression in breast tumors. The use of gene or protein data not specific for breast cancer did not reveal overlaps. According to the predicted G × G, experimental assays demonstrated functional interplay between lipoma-preferred partner and transforming growth factor-β signaling in the MCF10A non-tumorigenic mammary epithelial cell model. Next, integration of pancreatic tumor gene expression profiles with pancreatic cancer G × G predicted from a GWAS corroborated the observations made for breast cancer risk (REs of 25-59%). The method presented here can potentially support the identification of genetic interactions associated with cancer risk, providing novel mechanistic hypotheses for carcinogenesis.

Generation of insulin-producing cells from rat mesenchymal stem cells using an aminopyrrole derivative XW4.4

Type 1 diabetes mellitus (T1DM), a multisystem disease with both biochemical and anatomical/structural consequences, is a major health concern worldwide. Pancreatic islet transplantation provides a promising treatment for T1DM. However, the limited availability of islet tissue or new sources of insulin producing cells (IPCs) that are responsive to glucose hinder this promising approach. Though slow, the development of pancreatic beta-cell lines from rodent or human origin has been steadily progressing. Bone marrow-derived mesenchymal stem cells (MSCs) are multipotent, culture-expanded, non-hematopoietic cells that are currently being investigated as a novel cellular therapy. The in vitro differentiation potential of IPCs has raised hopes for a treatment of clinical diseases associated with autoimmunity.We screened for small molecules that induce pancreatic differentiation of IPCs. There are some compounds which showed positive effects on the DTZ staining. The aminopyrrole derivative compound XW4.4 which shows the best activity among them was found to induce pancreatic differentiation of rat MSCs (rMSCs). The in vitro studies indicated that treatment of rMSCs with compound XW4.4 resulted in differentiated cells with characteristics of IPCs including islet-like clusters, spherical, grape-like morphology, insulin secretion, positive for dithizone, glucose stimulation and expression of pancreatic endocrine cell marker genes. The data has also suggested that hepatocyte nuclear factor 3β (HNF 3β) may be involved in pancreatic differentiation of rMSCs when treated with XW4.4. Results indicate that XW4.4 induced rMSCs support the efforts to derive functional IPCs and serve as a means to alleviate limitations surrounding islet cell transplantation in the treatment of T1DM.

Metformin enhances glucagon-like peptide 1 via cooperation between insulin and Wnt signaling

One aspect of the effects of metformin on glucagon-like peptide (GLP)-1 might be associated with the mechanism by which the cross talk between insulin and Wnt signaling enhances GLP1 secretion, due to the action of metformin as an insulin sensitizer. However, this remains completely unknown. In this study, we have investigated the mechanisms of the action of metformin on cross talk between insulin and Wnt signaling. GLP1 enhancement by meformin was determined in human NCI-H716 intestinal L-cells and hyperglycemic db/db mice treated with metformin (0.25 and 0.5 mM and/or 12.5 mg/kg body weight) for 24 h and 2 months. Metformin increased GLP1 secretion in L-cells and db/db mice. Metformin stimulated the nuclear translocation of β-catenin and TOPflash reporter activity, and gene depletion of β-catenin or enhancement of mutation of transcription factor 7-like 2 binding site offset GLP1. In addition, insulin receptor substrate 2 gene depletion blocked metformin-enhanced β-catenin translocation. These effects were preceded by an increase in glucose utilization and calcium influx, the activation of calcium-dependent protein kinase, and, in turn, the activation of insulin signaling, and the inhibition of glycogen synthase kinase 3β, a potent inhibitor of β-catenin. Furthermore, high blood glucose levels were controlled via GLP1 receptor-dependent insulinotropic pathways in db/db mice, which were evidenced by the increase in GLP1 and insulin levels at 30 min after oral glucose loading and pancreatic insulinotropic gene expression. Our findings indicate that the cooperation between Wnt and its upstream insulin signaling pathways might be a novel and important mechanism underlying the effects of metformin on GLP1 production.

Beneficial effect of melatonin treatment on age-related insulin resistance and on the development of type 2 diabetes.

Abstract This paper will review the effect of aging on glucose metabolism and insulin resistance in pancreas and in peripheral tissues and how melatonin administration could affect these parameters. In SAMP8 mice insulin levels in plasma were found to be increased together with enhanced HOMA-IR values, whereas insulin content in pancreas showed a decrease with aging. Aging in SAMP8 mice was also associated with a significant increase in the relative expression of both protein and mRNA of different pro-inflammatory mediators. Furthermore, aging was associated with a decrease in the expression of Pdx-1, FoxO 1 and FoxO 3A and Sirt 1 in pancreas SAMP8 samples. Melatonin administration was able to reduce these age-related alterations, decreasing plasma insulin levels and increasing its pancreatic content in SAMP8 mice. HOMA-IR was decreased with melatonin treatment in all animals. Conversely, in SAMP8 mice, melatonin treatment decreased the expression of glucagon, GLUT2, somatostatin and insulin. Furthermore it was also able to increase the expression of Sirt 1, Pdx-1 and FoxO 3A. The present study has shown that aging is associated with significant alterations in the relative expression of pancreatic genes involved in both insulin secretion and glucose metabolism and that these are associated with an increase in inflammation and oxidative stress. Melatonin administration was able to reduce oxidative stress and inflammation and thus to improve pancreatic function in old mice. By doing so, insulin resistance is diminished and plasma insulin is reduced, enhancing insulin pancreatic content and reducing plasma glucose levels and HOMA index.

Programming of human umbilical cord mesenchymal stem cells in vitro to promote pancreatic gene expression

Human umbilical cord mesenchymal stem cells (HUMSCs) are candidates for tissue engineering and may potentially be used for transdifferentiation into pancreatic endocrine cells. The adenoviral vector is effective in transducing genes into stem cells that are refractory to gene delivery by non‑viral approaches. qPCR was used to detect the pancreatic endogenous gene expression of HUMSCs transfected by islet cell-specific transcription factors (TFs). In the present study, using adenoviruses, the mouse TFs, pancreatic and duodenal homeobox 1 (pdx1), V-maf musculoaponeurotic fibrosarcoma oncogene homolog A (mafa) and class B basic helix‑loop‑helix factor neurogenin 3 (ngn3), which are essential for pancreatic cell development, were introduced into HUMSCs to assess the expression of the pancreatic genes, glucagon, pdx1 and nk2 homeobox 2 (nkx2.2). When pdx1, mafa and ngn3 were cotransduced into HUMSCs, the expression of glucagon increased by 21‑fold at days 3 and 7 following transduction, while the endogenous pdx1 gene expression was increased by 15‑fold at day 3 and decreased by 70% at day 7. When mafa and ngn3 were cotransduced into HUMSCs, there was a 5‑fold increase in pdx1 gene expression at day 7, but no activation was observed at day 3. When mafa alone was introduced into HUMSCs, the pdx1 gene expression was elevated by 6‑fold at day 3 and decreased by 3‑fold at day 7. Transduction of ngn3 alone into HUMSCs induced nkx2.2 gene expression at day 3 but the expression levels were decreased at day 7. However, when pdx1 and ngn3 were cotransduced into HUMSCs, the expression levels of glucagon, pdx1 and nks2.2 were all lower than those observed with pdx1 or ngn3 transduction alone. These results suggested that the transduction of pdx1, mafa and ngn3 genes into HUMSCs induced the expression of the pancreatic genes, glucagon, pdx‑1 and nkx2.2, and that the expression was time dependent. In addition, different combinations of the TFs may demonstrate synergistic or antagonistic effects. This data may be beneficial for guiding future studies obtaining mature pancreatic endocrine cells from HUMSCs.

Extracellular matrix composition significantly influences pancreatic stellate cell gene expression pattern: role of transgelin in PSC function

Activated pancreatic stellate cells (PSCs) are responsible for the fibrotic matrix of chronic pancreatitis and pancreatic cancer. In vitro protocols examining PSC biology have usually involved PSCs cultured on plastic, a nonphysiological surface. However, PSCs cultured on physiological matrices, e.g., Matrigel (normal basement membrane) and collagen (fibrotic pancreas), may have distinctly different behaviors compared with cells cultured on plastic. Therefore, we aimed to 1) compare PSC gene expression after culture on plastic, Matrigel, and collagen I; 2) validate the gene array data for transgelin, the most highly dysregulated gene in PSCs grown on activating vs. nonactivating matrices, at mRNA and protein levels; 3) examine the role of transgelin in PSC function; and 4) assess transgelin expression in human chronic pancreatitis sections. Culture of PSCs on different matrices significantly affected their gene expression pattern. 146, 619, and 432 genes, respectively, were differentially expressed (P < 0.001) in PSCs cultured on collagen I vs. Matrigel, Matrigel vs. plastic, and collagen I vs. plastic. The highest fold change (12.5-fold upregulation) in gene expression in cells on collagen I vs. Matrigel was observed for transgelin (an actin stress fiber-associated protein). Transgelin was significantly increased in activated PSCs vs. quiescent PSCs. Silencing transgelin expression decreased PSC proliferation and also reduced platelet-derived growth factor-induced PSC migration. Notably, transgelin was highly expressed in chronic pancreatitis in stromal areas and periacinar spaces but was absent in acinar cells. These findings suggest that transgelin is a potentially useful target protein to modulate PSC function so as to ameliorate pancreatic fibrosis.

Differences in the Degree of Cerulein-Induced Chronic Pancreatitis in C57BL/6 Mouse Substrains Lead to New Insights in Identification of Potential Risk Factors in the Development of Chronic Pancreatitis

A frequently used experimental model of chronic pancreatitis (CP) recapitulating human disease is repeated injection of cerulein into mice. C57BL/6 is the most commonly used inbred mouse strain for biomedical research, but widespread demand has led to generation of several substrains with subtly different phenotypes. In this study, two common substrains, C57BL/6J and C57BL/6NHsd, exhibited different degrees of CP, with C57BL/6J being more susceptible to repetitive cerulein-induced CP as assessed by pancreatic atrophy, pancreatic morphological changes, and fibrosis. We hypothesized that the deficiency of nicotinamide nucleotide transhydrogenase (NNT) protein in C57BL/6J is responsible for the more severe C57BL/6J phenotype but the parameters of CP in NNT-expressing transgenic mice generated on a C57BL6/J background do not differ with those of wild-type C57BL/6J. The highly similar genetic backgrounds but different CP phenotypes of these two substrains presents a unique opportunity to discover genes important in pathogenesis of CP. We therefore performed whole mouse genome Affymetrix microarray analysis of pancreatic gene expression of C57BL/6J and C57BL/6NHsd before and after induction of CP. Genes with differentially regulated expression between the two substrains that might be candidates in CP progression included Mmp7, Pcolce2, Itih4, Wdfy1, and Vtn. We also identified several genes associated with development of CP in both substrains, including RIKEN cDNA 1810009J06 gene (trypsinogen 5), Ccl8, and Ccl6.

The involvement of interleukin-22 in the expression of pancreatic beta cell regenerative Reg genes.

BackgroundIn Type 1 diabetes, the insulin-producing β-cells within the pancreatic islets of Langerhans are destroyed. We showed previously that immunotherapy with Bacillus Calmette-Guerin (BCG) or complete Freund’s adjuvant (CFA) of non-obese diabetic (NOD) mice can prevent disease process and pancreatic β-cell loss. This was associated with increased islet Regenerating (Reg) genes expression, and elevated IL-22-producing Th17 T-cells in the pancreas.ResultsWe hypothesized that IL-22 was responsible for the increased Reg gene expression in the pancreas. We therefore quantified the Reg1, Reg2, and Reg3δ (INGAP) mRNA expression in isolated pre-diabetic NOD islets treated with IL-22. We measured IL-22, and IL-22 receptor(R)-α mRNA expression in the pancreas and spleen of pre-diabetic and diabetic NOD mice. Our results showed: 1) Reg1 and Reg2 mRNA abundance to be significantly increased in IL-22-treated islets in vitro; 2) IL-22 mRNA expression in the pre-diabetic mouse pancreas increased with time following CFA treatment; 3) a reduced expression of IL-22Rα following CFA treatment; 4) a down-regulation in Reg1 and Reg2 mRNA expression in the pancreas of pre-diabetic mice injected with an IL-22 neutralizing antibody; and 5) an increased islet β-cell DNA synthesis in vitro in the presence of IL-22.ConclusionsWe conclude that IL-22 may contribute to the regeneration of β-cells by up-regulating Regenerating Reg1 and Reg2 genes in the islets.

Reprogrammed pancreatic progenitor-like intermediate state of hepatic cells is more susceptible to pancreatic beta cell differentiation

Induced pluripotent stem cells (iPSCs) hold great promise for cell therapy. However, their low efficiency of lineage-specific differentiation and tumorigenesis severely hinder clinical translation. We hypothesized that reprogramming of somatic cells into lineage-specific progenitor cells might allow for large-scale expansion, avoiding the tumorigenesis inherent with iPSCs and simultaneously facilitating lineage-specific differentiation. Here we aimed at reprogramming rat hepatic WB cells, using four Yamanaka factors, into pancreatic progenitor cells (PPCs) or intermediate (IM) cells that have characteristics of PPCs. IM clones were selected based on their specific morphology and alkaline phosphatase activity and stably passaged under defined culture conditions. IM cells did not have iPSC properties, could be stably expanded in large quantity, and expressed all 14 genes that are used to define the PPC developmental stage. Directed differentiation of IM and WB cells by Pdx1-Ngn3-MafA (PNM) into pancreatic beta-like cells revealed that the IM cells are more susceptible to directed beta cell differentiation because of their open chromatin configuration, as demonstrated by expression of key pancreatic beta cell genes, secretion of insulin in response to glucose stimulation, and easy access to exogenous PNM proteins at the rat insulin 1 and Pdx1 promoters. This notion that IM cells are superior to their parental cells is further supported by the epigenetic demonstration of accessibility of Pdx1 and insulin 1 promoters. In conclusion, we have developed a strategy to derive and expand PPC cells from hepatic WB cells using conventional cell reprogramming. This proof-of-principal study may offer a novel, safe and effective way to generate autologous pancreatic beta cells for cell therapy of diabetes.

Involvement of Nuclear Factor Kappa B in High-Fat Diet-Related Pancreatic Fibrosis in Rats

Background/AimsHigh-fat diets contribute to pancreatic fibrogenesis, but the pathogenesis remains unclear. This study investigated the role of nuclear factor kappa B (NF-κB) in high-fat diet-induced pancreatic fibrosis in rats.MethodsMale Wistar rats were fed a high-fat diet or standard normal chow for 20 weeks. Pancreatic fibrosis was determined by Sirius red staining. Immunohistochemical staining, reverse transcription-polymerase chain reaction and Western blotting were used to identify NF-κB-associated genes or protein expressions.ResultsInflammation, fat deposition, pancreatic stellate cell activation and fibrosis were observed in the pancreases of the high-fat diet group. NF-κB subunit p65 (NF-κB/p65) expression was localized to the nucleus, and intercellular adhesion molecule 1 (ICAM-1) was over-expressed. Pancreatic gene expression levels of NF-κB/p65, ICAM-1 and tumor necrosis factor α were all elevated significantly in rats fed a high-fat diet compared with control rats. Western blotting also revealed significantly increased levels of ICAM-1 and nuclear NF-κB/p65 in rats fed high-fat diets comparison with control rats.ConclusionsNF-κB is involved in high-fat diet-related pancreatic fibrosis.

Abstract 203: Hotair, a long non-coding RNA, exhibits pro-oncogenic activity in pancreatic cancer

Abstract HOTAIR is a long intervening non-coding RNA (lincRNA) that represses specific gene transcription by interaction with the Polycomb Repressive Complex 2 (PRC2) that trimethylates histone H3 lysine 27, leading to reprograming of chromatin states. HOTAIR is a poor prognostic indicator for survival of breast, colon and liver cancer patients and is highly associated with cancer invasion and metastasis. In this study, we show that HOTAIR is more highly expressed in pancreatic tumors than normal tissue and is strongly correlated not only with cell invasiveness but also cell proliferation and death. Overexpression of HOTAIR increased cell invasion in pancreatic cancer cells expressing low levels of HOTAIR and this was previously observed in other cancer cell lines. However, unlike previous reports, HOTAIR knockdown in Panc1 and L3.6pL pancreatic cancer cells that overexpress this lincRNA decreased cell proliferation, altered cell cycle progression, and induced apoptosis, demonstrating an expanded function for HOTAIR in pancreatic cancer cells compared to other cancer cell lines. Results of gene profiling studies after HOTAIR knockdown showed that there was minimal overlap between HOTAIR-regulated genes in pancreatic vs. breast cancer cells and HOTAIR uniquely suppressed several interferon-related genes and genes related to cell cycle progression in pancreatic cancer cells. Consistently, Gene Set Enrichment Analysis (GSEA) shows that HOTAIR regulates gene sets relevant to cell proliferation using HOTAIR Knockdown gene profiling data and pancreatic patient gene expression data. Analysis of selected genes suppressed by HOTAIR in Panc1 and L3.6 pL cells showed by knockdown of EZH2 and chromatin immunoprecipitation assays that HOTAIR-mediated gene repression was both PRC-2-dependent and -independent. HOTAIR knockdown in L3.6pL cells also inhibited tumor growth in mouse xenograft model, further demonstrating the pro-oncogenic function of HOTAIR in pancreatic cancer. These results indicated that HOTAIR is a potential molecular target for inhibiting pancreatic cancer cell invasion, metastasis and proliferation for inducing cell death. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 203. doi:1538-7445.AM2012-203

Abstract 2186: Function and regulation of Polo-like Kinase 3 in human pancreatic cancer

Abstract Pancreatic cancer is currently the fourth leading cause of cancer death in the United States. Despite the recent advances in pancreatic cancer research, patients with this devastating disease still have a poor prognosis. Therefore, deciphering pancreatic cancer-related gene expression and defining the individual gene's specific functions will make a significant impact on the diagnosis and treatment of pancreatic cancer. Recently, our lab has demonstrated the tumorigenic transformation in an immortalized pancreatic cell line, HPNE/hTERT by sequential introduction of multiple genetic alterations. We found that Polo-like kinase 3 (Plk3) is significantly down-regulated in transformed tumor cell lines. Plk3 belongs to the Polo-like kinase family and is a multi-functional kinase. We previously reported that Plk3 played a pro-apoptotic role in pancreatic cancer lines when it was overexpressed. Plk3 down-regulation in transformed HPNE cells suggests that Plk3 may have tumor suppression function during pancreatic tumor development. In addition, we found Plk3 expression is regulated by Pten. In Pten-knockout MEF cells, Plk3 expression was significantly down-regulated. So Plk3 may be downstream of Pten in the tumor suppression pathway. These data suggest that Plk3 play an important role in pancreatic cancer development. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2186. doi:1538-7445.AM2012-2186

Accelerated Proliferation and Differential Global Gene Expression in Pancreatic Islets of Five-Week-Old Heterozygous Men1 Mice: Men1 Is a Haploinsufficient Suppressor

Individuals carrying heterozygous (hz) MEN1 (Multiple Endocrine Neoplasia Syndrome Type 1) germ line mutations develop endocrine tumors as a result of somatic loss of the wild-type (wt) allele. However, endocrine cell proliferation has been observed despite wt allele retention, indicating haploinsufficiency. To study downstream molecular effects of the hz haplotype, a germ line Men1 hz mouse model was used to explore differences in global endocrine pancreatic gene expression. Because islet cells of 5-wk-old hz mice express Menin from the retained wt Men1 allele, these were isolated after collagenase digestion of the pancreas, and used for global gene expression array. Wild-type littermates were used for comparison. Array findings were corroborated by quantitative PCR, Western blotting, in situ proximity ligation assay, and immunohistochemistry. The hz islets show increased proliferation: the Ki-67 index was twice as high as in wt islets (3.48 vs. 1.74%; P = 0.024). The microarray results demonstrated that several genes were differentially expressed. Some selected genes were studied on the protein level, e.g. the cytoskeletal regulator myristoylated alanine-rich protein kinase C substrate (Marcks) was significantly less expressed in hz islets, using in situ proximity ligation assay and Western blotting (P < 0.001 and P < 0.01, respectively). Further, gene ontology analysis showed that genes with higher mRNA expression in the hz endocrine pancreas were associated with e.g. chromatin maintenance and apoptosis. Lower mRNA was observed for genes involved in growth factor binding. In conclusion, despite retained Menin expression, proliferation was accelerated, and numerous genes were differentially expressed in the endocrine pancreas of 5-wk-old hz Men1 mice, corroborating the hypothesis that MEN1 is a haploinsufficient suppressor.

Identification of Novel Type 1 Diabetes Candidate Genes by Integrating Genome-Wide Association Data, Protein-Protein Interactions, and Human Pancreatic Islet Gene Expression

Genome-wide association studies (GWAS) have heralded a new era in susceptibility locus discovery in complex diseases. For type 1 diabetes, >40 susceptibility loci have been discovered. However, GWAS do not inevitably lead to identification of the gene or genes in a given locus associated with disease, and they do not typically inform the broader context in which the disease genes operate. Here, we integrated type 1 diabetes GWAS data with protein-protein interactions to construct biological networks of relevance for disease. A total of 17 networks were identified. To prioritize and substantiate these networks, we performed expressional profiling in human pancreatic islets exposed to proinflammatory cytokines. Three networks were significantly enriched for cytokine-regulated genes and, thus, likely to play an important role for type 1 diabetes in pancreatic islets. Eight of the regulated genes (CD83, IFNGR1, IL17RD, TRAF3IP2, IL27RA, PLCG2, MYO1B, and CXCR7) in these networks also harbored single nucleotide polymorphisms nominally associated with type 1 diabetes. Finally, the expression and cytokine regulation of these new candidate genes were confirmed in insulin-secreting INS-1 β-cells. Our results provide novel insight to the mechanisms behind type 1 diabetes pathogenesis and, thus, may provide the basis for the design of novel treatment strategies.

Melatonin can improve insulin resistance and aging-induced pancreas alterations in senescence-accelerated prone male mice (SAMP8)

The aim of the present study was to investigate the effect of aging on several parameters related to glucose homeostasis and insulin resistance in pancreas and how melatonin administration could affect these parameters. Pancreas samples were obtained from two types of male mice models: senescence-accelerated prone (SAMP8) and senescence-accelerated-resistant mice (SAMR1). Insulin levels in plasma were increased with aging in both SAMP8 and SAMR1 mice, whereas insulin content in pancreas was decreased with aging in SAMP8 and increased in SAMR1 mice. Expressions of glucagon and GLUT2 messenger RNAs (mRNAs) were increased with aging in SAMP8 mice, and no differences were observed in somatostatin and insulin mRNA expressions. Furthermore, aging decreased also the expressions of Pdx-1, FoxO 1, FoxO 3A and Sirt1 in pancreatic SAMP8 samples. Pdx-1 was decreased in SAMR1 mice, but no differences were observed in the rest of parameters on these mice strains. Treatment with melatonin was able to decrease plasma insulin levels and to increase its pancreatic content in SAMP8 mice. In SAMR1, insulin pancreatic content and plasma levels were decreased. HOMA-IR was decreased with melatonin treatment in both strains of animals. On the other hand, in SAMP8 mice, treatment decreased the expression of glucagon, GLUT2, somatostatin and insulin mRNA. Furthermore, it was also able to increase the expression of Sirt1, Pdx-1 and FoxO 3A. According to these results, aging is associated with significant alterations in the relative expression of pancreatic genes associated to glucose metabolism. This has been especially observed in SAMP8 mice. Melatonin administration was able to improve pancreatic function in old SAMP8 mice and to reduce HOMA-IR improving their insulin physiology and glucose metabolism.

Islet microarchitecture and glucose transporter expression of the pancreas of the marmoset monkey display similarities to the human

The common marmoset New World monkey (Callithrix jacchus), is a primate model with great potential for scientific research, including research on diabetes. However, in opposite to Rhesus and Java monkeys (Macaca mulatta and Macaca fascicularis) little is known about the marmosets islet microarchitecture, glucose transporter and pancreatic marker gene expression. In this work we analyze differences and similarities in size, shape, cellular composition and intra-islet topography between the common marmoset and the human endocrine pancreas. Different sized, circular and a-circular shaped islets of the common marmoset and human display α-cells in the whole islet organ leading to a ribbon-like islet type. The number of islets was significantly higher in the common marmoset compared with humans. However, the area of insulin-producing cells was significantly higher in the human pancreas. Intra-islet distribution pattern of δ- and β-cells was similar in both species. The morphology of the exocrine pancreas regarding acinar and ductal cells was quite similar as confirmed by ultrastructural analysis. Additionally the ultrastructure of secretory granules from α-, δ- and β-cells of human and non-human primate pancreas showed the same characteristics. Molecular analysis showed the presence of endocrine pancreatic marker genes like PMCA2, NCX1, SUR1, KIR6.2, MAFA, NGN3 and PDX1 also expressed in the human. For the first time we could show presence of Glut 5 and 9 transporters in addition to the low abundance transporter Glut2 and the highly expressed Glut1 glucose transporter. We propose that Callithrix jacchus displays a new animal model for diabetes research and regenerative medicine.

Glucose-induced nuclear shuttling of ChREBP is mediated by sorcin and Ca(2+) ions in pancreatic β-cells.

Carbohydrate-responsive element-binding protein (ChREBP) is a regulator of pancreatic β-cell gene expression and an important mediator of glucotoxicity. Glucose increases the activity and nuclear localization of ChREBP by still ill-defined mechanisms. Here we reveal, using both MIN6 and primary mouse β-cells, a unique mechanism behind ChREBP nuclear translocation. At low glucose concentrations, ChREBP interacts with sorcin, a penta EF hand Ca2+ binding protein, and is sequestered in the cytosol. Sorcin overexpression inhibits ChREBP nuclear accumulation at high glucose and reduced the activity of L-type pyruvate kinase (L-PK) and TxNIP promoters, two well-characterized ChREBP target genes. Sorcin inactivation by RNA interference increases ChREBP nuclear localization and in vivo binding to the L-PK promoter at low glucose concentrations. Ca2+ influx was essential for this process since Ca2+ chelation with EGTA, or pharmacological inhibition with diazoxide and nifedipine, blocked the effects of glucose. Conversely, mobilization of intracellular Ca2+ with ATP caused the nuclear accumulation of ChREBP. Finally, sorcin silencing inhibited ATP-induced increases in intracellular Ca2+ and glucose-stimulated insulin secretion. We therefore conclude that sorcin retains ChREBP in the cytosol at low glucose concentrations and may act as a Ca2+ sensor for glucose-induced nuclear translocation and the activation of ChREBP-dependent genes.

Vitamin E Alters Inflammatory Gene Expression in Alcoholic Chronic Pancreatitis

Objective: To evaluate the effect of vitamin E supplementation on pancreatic gene expression of inflammatory markers in rats with alcoholic chronic pancreatitis. Methods: Wistar rats were divided into 3 groups: control (1), alcoholic chronic pancreatitis without (2) and with (3) vitamin E supplementation. Pancreatitis was induced by a liquid diet containing ethanol, cyclosporin A and cerulein. α-tocopherol content in plasma and liver and pancreas histopathology were analyzed. Gene expression of inflammatory biomarkers was analyzed by the quantitative real-time PCR technique. Results: The animals that received vitamin E supplementation had higher α-tocopherol amounts in plasma and liver. The pancreas in Group 1 showed normal histology, whereas in Groups 2 and 3, mild to moderate tissue destruction foci and mononuclear cell infiltration were detected. Real-time PCR analysis showed an increased expression of all genes in Groups 2 and 3 compared to Group 1. Vitamin E supplementation decreased the transcript number of 5 genes (α-SMA, COX-2, IL-6, MIP-3α and TNF-α) and increased the transcript number of 1 gene (Pap). Conclusion: Vitamin E supplementation had anti-inflammatory and beneficial effects on the pancreatic gene expression of some inflammatory biomarkers in rats with alcoholic chronic pancreatitis, confirming its participation in the inflammatory response mechanisms in the pancreas.

Meta-analysis of genome-wide association studies identifies eight new loci for type 2 diabetes in east Asians.

We conducted a three-stage genetic study to identify susceptibility loci for type 2 diabetes (T2D) in east Asian populations. We followed our stage 1 meta-analysis of eight T2D genome-wide association studies (6,952 cases with T2D and 11,865 controls) with a stage 2 in silico replication analysis (5,843 cases and 4,574 controls) and a stage 3 de novo replication analysis (12,284 cases and 13,172 controls). The combined analysis identified eight new T2D loci reaching genome-wide significance, which mapped in or near GLIS3, PEPD, FITM2-R3HDML-HNF4A, KCNK16, MAEA, GCC1-PAX4, PSMD6 and ZFAND3. GLIS3, which is involved in pancreatic beta cell development and insulin gene expression, is known for its association with fasting glucose levels. The evidence of an association with T2D for PEPD and HNF4A has been shown in previous studies. KCNK16 may regulate glucose-dependent insulin secretion in the pancreas. These findings, derived from an east Asian population, provide new perspectives on the etiology of T2D.